The A2F10 monoclonal antibody reacts with mouse CD135, also known as Flk2/Flt3. A member of the tyrosine kinase receptor family, this 135-150kDa molecule is expressed by primitive progenitor cells in fetal liver and adult bone marrow. Two-color staining of adult mouse bone marrow cells with A2F10 and RA3-6B2 (CD45R/B220) or M1/70 (CD11b) reveals Flk-2-positive subpopulations of B cells or myeloid cells, respectively.